A drywall joint refers to a combination of a drywall tape imbedded in a joint compound to repair drywall or to cover an open seam in the drywall. Drywall refers to panels or sections of building materials, including, but not limited to, gypsum board and cement board. The sections of drywall are secured against a framework of vertical studs that have been erected as part of a wall in a building, including a fixed or transportable building. When a drywall ceiling is desired, additional drywall sections are installed against a framework of ceiling joists to provide a drywall ceiling. Narrow openings in the form of seams are visible between opposed edges of the drywall sections, whether the opposed edges meet along the plane of a wall or ceiling or whether the opposed edges meet at an inside corner. Additional openings in the drywall sections are caused by damage to the drywall surface and are in need of repair. Such openings are to be covered by drywall joints, such that the drywall appears to be seamless.
A drywall joint is constructed by hand or by machine. In constructing the drywall joint, the opening is filled with a water containing joint compound, also known as a drywall compound. Nails, screws and like fasteners that secure the drywall sections to the framework are driven into the drywall sections until the fastener heads are recessed below the surfaces of the drywall sections. The fastener heads are covered by the joint compound. While filling the opening, a thin layer of the joint compound is spread a few centimeters wide onto the drywall surfaces adjacent to the filled opening. A length of drywall tape is applied by hand or by machine to bridge across the filled opening and adhere onto the thin layer. The thin layer is at least as wide as the drywall tape to adhere an entire width of the drywall tape to the drywall sections. After drying the thin layer, at least one layer, a second layer, of the joint compound is applied to cover the drywall tape. The second layer is applied, and then spread out, smoothed and shaped with a trowel, referred to as a drywall knife or blade, wielded by hand or by machine, to blend smoothly coplanar with the surfaces of the drywall sections, such that the drywall joint hides the opening, and the drywall sections visibly appear to be seamless. The drywall joint blends smoothly with the surfaces of the drywall sections and is substantially concealed thereby. After drying the second layer, the surface of the joint compound is lightly sanded with fine grit sandpaper to smooth the surface. Alternatively, the sanding operation follows an optional application of joint compound to touch up imperfections in the second layer. Similar drywall joints are constructed to cover openings caused by damage to the drywall.
U.S. Pat. No. 4,042,739 discloses a paper drywall tape having an adhesive on one side of the paper tape. The adhesive is wetted, applied against drywall, and dried. Thus, the drywall tape is directly adhered to the drywall by the adhesive. Once the adhesive is dried, the adhesive becomes impervious to water. When a drywall compound is applied to cover the drywall tape, the water present in the drywall compound has no effect on the adhesive. A paper tape has a desirable, low profile thickness, of approximately 0.25 mm. However, holes through the paper are required to expel air bubbles, which holes reduce the strength of the drywall tape. A top layer of joint compound is applied to cover the paper tape. The paper tape separates the top layer from the remainder of the drywall joint, which prevents the top layer of joint compound from penetrating the paper tape and bonding to the remainder of the drywall joint. The top layer is susceptible to forming a crack over the passage of time. A paper tape is susceptible to mold and mildew growth in a humid environment, such as, in kitchens, bathrooms and rooms below earth grade.
A drywall tape in the form of a mesh or web of high strength fibers is commercially available as Fibatape® self adhesive fiberglass mesh. The mesh or web is porous to the joint compound, which allows a top layer of the joint compound to penetrate through the mesh or web and bond with a remainder of the drywall joint located under the drywall tape. Consequently, a bottom layer and a top layer of joint compound are stronger than if the web or mesh would not allow the joint compound to penetrate through the mesh or web. However, the mesh or web has fibers of about 0.31 mm. thickness or diameter, which is relied upon for fiber strength. Because the web or mesh is thicker than a paper drywall tape of 0.25 mm. thickness, a thicker amount of drywall compound is required to construct a drywall joint that covers the mesh. Further, the joint compound must be applied with sufficient thickness to fill interstices in the thickness of the web. A generous thickness is to be avoided, since a generous thickness produces an undesired, raised bump visible on the surface of the drywall sections. It would be desirable for the drywall tape to have thinner fibers to reduce the thickness of joint compound necessary for covering the fibers. However, thinner fibers have been avoided in the past, since thinner fibers have less strength than thicker fibers and would provide weaker reinforcement of the drywall joint.
Application U.S. 2003-0181114 discloses a drywall tape in the form of a web of high strength fibers, having a water soluble resinous coating thereon. The resinous coating is soluble in a water containing joint compound, and forms an adhesive bond with said joint compound when dried. The adhesive coated fibers resist pull out from the joint compound when dried. To obtain adequate fiber strength, the fibers are thicker than a paper tape. Further, the fibers cross over one another to form fiber crossovers in the web. Such crossovers appear at the web surface such that, when a layer of joint compound is applied to cover the web, the web surface has a bumpy surface texture or topography that impedes the spreading out, smoothing and shaping of the joint compound by use of a trowel. Thus, it would be desirable for the drywall tape to have a surface texture or topography that is substantially free of fiber crossovers that would impede the smoothing and shaping of the surface of the joint compound.
U.S. Pat. No. 6,054,205 discloses a cement board reinforced by embedding a facing sheet between two layers of cementitious material. The facing sheet has an open mesh glass screen and a melt blown polymer web. Formation of the web by a melt blowing process melts the web to form a microporous surface that is water resistant and consequently impenetrable by a cementitious material containing water. Further, a thick layer of cementitious material is applied onto the water resistant surface, which deeply embeds the web, but can not penetrate the water resistant surface or form a bond therewith. The facing sheet is suitable for deep embedment within a relatively thick cement board, but is unsuitable for embedment in a thin layer of drywall compound, since a thin layer would lack penetration of such a facing sheet, and would lack formation of a bond with such a facing sheet.